There are many devices which redirect or turn the flow of a fluid to achieve such fluid flow redirection in an efficient manner. For example, devices such as jet engine inlet guide vanes, air conditioning ducting, and automobile spoilers operate to redirect the flow of air for various purposes. However, it is generally desirable to redirect the fluid flow in a manner that flow pressure losses and turbulence are minimized.
An application in which it is important to maximize air turning efficiency (and minimize turbulence) is in the area of wind tunnels. In a typical wind tunnel a model to be tested is placed in the wind tunnel and measurements are made of the airflow over the model-under-test. The wind tunnel typically is a closed rectangular tube inside of which air is driven by a large fan. At each of the four corners of the wind tunnel the air is turned through a ninety degree bend. In addition, it is important that the airflow delivered to the model-under-test be uniform.
In conventional wind tunnels, turning vanes are provided at the corners of the wind tunnel to help direct the air around the corners in a manner to maximize turning efficiency and to minimize turbulence. However, even in these conventional wind tunnels which use conventional turning vanes the turbulence and nonuniform flow of the air can be substantial.
A number of conventional airflow turning devices have been disclosed. For example, U.S. Pat. No. 2,735,612 by Hausmann discloses airfoil shaped vanes for improving air flow in passages. In addition, U.S. Pat. No. 1,996,596 by Smith Jr. discloses a fluid duct having a number of curved blades for reducing turbulence at bends and elbows of the duct. Furthermore, U.S. Pat. No. 2,662,553 by Dimmock discloses duct elbows for gaseous fluid flow systems wherein a number of curved blades are located at the elbow for improving flow through the elbows. And also, U.S. Pat. No. 2,813,708 by Frey discloses curved flow bodies for improving flow characteristics at bends in brick-lined furnaces.